Science News shares an analysis of the human hippocampus from a computer-designer’s standpoint, finding that though the network of brain-cell connections are relatively sparse, those few cells that do connect with others have lots and lots of connections — a state of affairs that actually maximizes the possible memory storage in the brain’s network:
Previously discovered differences between mouse and human hippocampi hinted that animals with more nerve cells may have fewer connections — or synapses — between them, says cellular neuroscientist Peter Jonas of the Institute of Science and Technology Austria in Klosterneuburg. To see if this held true, he and his colleagues examined tissue taken with consent from eight patients who underwent brain surgery to treat epilepsy.
Recording electrical activity from human pyramidal cells in the CA3 area suggested that about 10 synapses existed for every 800 cell pairs tested. In mice, that concentration roughly tripled. Despite the relatively scant nerve cell connections in humans, those cells showed steady and robust activity when sending signals to one another — unlike mouse pyramidal cells.
Consistent with the setup in humans, mathematical modeling suggested that an abundance of nerve cells combined with sparse but strong connections is a design that maximizes memory retrieval and storage.
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You can read more about the hippocampus neural-network research here, in Cell.